CVE-2026-33271: Acronis True Image Privilege Escalation

CVE-2026-33271 Overview

CVE-2026-33271 is a local privilege escalation vulnerability affecting Acronis True Image for Windows. The vulnerability stems from insecure folder permissions that can be exploited by a local attacker with limited privileges to escalate their access to higher privilege levels on the affected system. This weakness is classified as CWE-732 (Incorrect Permission Assignment for Critical Resource).

Critical Impact

Local attackers with low privileges can exploit insecure folder permissions to gain elevated access, potentially compromising confidentiality, integrity, and availability of the affected Windows system.

Affected Products

• Acronis True Image (Windows) before build 42902

Discovery Timeline

• April 2, 2026 - CVE-2026-33271 published to NVD
• April 2, 2026 - Last updated in NVD database

Technical Details for CVE-2026-33271

Vulnerability Analysis

This vulnerability involves incorrect permission assignment for critical resources within Acronis True Image on Windows systems. The application fails to properly restrict access to one or more folders, allowing users with lower privileges to interact with protected resources in unintended ways. The local attack vector requires user interaction for exploitation, though successful exploitation can lead to complete compromise of confidentiality, integrity, and availability on the affected system.

The insecure folder permissions create a scenario where a local attacker can potentially modify, replace, or inject malicious content into directories that should be protected. This is particularly concerning in backup software like Acronis True Image, which often runs with elevated privileges to access system files and manage backup operations.

Root Cause

The root cause of CVE-2026-33271 is CWE-732: Incorrect Permission Assignment for Critical Resource. The application installs or creates folders with overly permissive access control lists (ACLs), allowing non-privileged users to write to directories that the application later accesses with elevated privileges. This creates a privilege escalation vector where attackers can plant malicious files or modify existing files that will be executed or loaded by the higher-privileged Acronis processes.

Attack Vector

The attack requires local access to the target system and necessitates user interaction for successful exploitation. A threat actor with low-privilege access to a Windows system running a vulnerable version of Acronis True Image could identify folders with weak permissions and leverage them to escalate privileges. The complexity of this attack is considered high, as it may require specific timing or conditions to successfully exploit the misconfigured permissions.

The attacker would typically need to:

1. Identify writable folders used by Acronis True Image
2. Place malicious content (such as DLLs, scripts, or configuration files) in these directories
3. Wait for or trigger the application to access the malicious content with elevated privileges

Detailed technical information about this vulnerability can be found in the Acronis Security Advisory SEC-9108.

Detection Methods for CVE-2026-33271

Indicators of Compromise

• Unexpected files or modifications in Acronis True Image installation directories
• Unauthorized changes to folder permissions on Acronis-related directories
• Unusual process spawning from Acronis True Image executables
• Event logs indicating permission changes on protected folders

Detection Strategies

• Monitor file system activity in Acronis True Image installation directories for unauthorized writes
• Implement file integrity monitoring (FIM) on critical application folders
• Audit Windows Security Event Logs for privilege escalation attempts (Event IDs 4672, 4673)
• Use endpoint detection tools to identify suspicious DLL loading or file replacement patterns

Monitoring Recommendations

• Enable Windows auditing for object access on Acronis True Image directories
• Configure alerts for any write operations to the application folder by non-administrative accounts
• Review Windows Event Viewer for Security events related to permission changes
• Deploy SentinelOne Singularity to detect and alert on privilege escalation behaviors

How to Mitigate CVE-2026-33271

Immediate Actions Required

• Update Acronis True Image for Windows to build 42902 or later immediately
• Audit folder permissions on existing Acronis True Image installations
• Review local user accounts for any signs of unauthorized privilege escalation
• Restrict local access to systems running vulnerable versions until patching is complete

Patch Information

Acronis has addressed this vulnerability in Acronis True Image for Windows build 42902. Organizations should update to this version or later to remediate the vulnerability. For complete patch details and download information, refer to the Acronis Security Advisory SEC-9108.

Workarounds

• Manually review and restrict folder permissions on Acronis True Image directories using Windows NTFS permissions
• Limit local user access to systems running vulnerable Acronis True Image versions
• Implement application whitelisting to prevent unauthorized executables from running in Acronis directories
• Use Windows Defender Application Control or similar tools to restrict code execution in affected folders

# Verify Acronis True Image folder permissions using PowerShell
Get-Acl "C:\Program Files (x86)\Acronis\TrueImageHome" | Format-List

# Review specific folder permissions for overly permissive settings
icacls "C:\Program Files (x86)\Acronis\TrueImageHome" /T